ANTIOCH — What caused a fatal crash over the weekend in which an Antioch man drove off an overpass may never be fully explained because of a lack of witness accounts, police said.

The accident occurred about 2:40 p.m. Sunday, when the driver of an eastbound vehicle on Wilbur Avenue lost control east of Apollo Court, went through an overpass railing and landed on railroad tracks below, police said. The driver, identified as 44-year-old Roberto Peralta, died that day.

Traffic Sgt. Robert Quintero said a lack of eyewitnesses and the driver’s inability to communicate with police before being transported to a hospital have left investigators with few answers. The Contra Costa County Coroner’s Office ruled out any medical condition that might have preceded the loss of vehicle control, and said Peralta died from injuries suffered in the crash.

“We may never really know. He lost control for an unknown reason,” Quintero said.

Robert Salonga is a Pulitzer Prize-winning reporter covering criminal justice and public safety for The Mercury News. A San Jose native, he attended UCLA and has a Master's degree in journalism from the University of Maryland. He previously reported in Washington, D.C., Salinas and the East Bay, and is a middling triathlete. Reach him the low-tech way at 408-920-5002.